1. Field of the Invention
The present invention relates, generally, to exhaust gas recirculation systems for internal combustion engines and, more specifically, to an improved exhaust gas recirculation system having an integrated vacuum regulator and delta pressure sensor.
2. Description of the Related Art
Exhaust gas recirculation (EGR) valves are employed to control the recirculation of a portion of the exhaust gas generated from an internal combustion engine flowing through the exhaust manifold back into the combustion chamber via the intake manifold. Recirculation of exhaust gases to the air/fuel mixture at the intake of the internal combustion engine is conducive to the reduction of the concentration of noxious nitrogen oxides in the exhaust gases which are discharged from the engine. Accordingly, and for this reason, exhaust gas recirculation is effected typically on gasoline engines when the engine is operating under part-throttle or substantial-throttle conditions. More specifically, during idling conditions, negligible amounts of nitrogen oxides are produced in the combustion chambers of the engine and, therefore, there is little or no need of recirculating exhaust gases to the air/fuel mixture. On the other hand, under part-throttle or substantial-throttle conditions, the throttle valve which controls intake air to the internal combustion engine is held in a more open position so that sufficient air may be add mixed to the fuel. At the same time, and during these operating conditions, it is common to recirculate exhaust gases into the air/fuel mixture and thereby reduce the noxious emissions of the internal combustion engine.
Diesel engines typically utilize EGR during no load (idle) through medium load. In virtually all cases, gasoline and diesel, EGR is shut off as full-load conditions are approached.
The operation of the EGR valve and thus the amount of exhaust gas recirculated is often controlled by an electrically actuated vacuum regulator (EVR) as well as a differential pressure sensor, also known as a delta pressure sensor. In turn, signals to and from these components are controlled by an engine control module (ECM). The effective control and simultaneous coordination of the various EGR components presents some difficult challenges. More specifically, it is important to precisely actuate the EGR valve so that NOx emissions may be optimally minimized. The more components employed to effectively implement exhaust gas recirculation the longer is the system response time and the more difficult and costly it is to control the process. In the related art, the EGR valve, EVR and delta pressure sensor are typically separate components mounted at various places on the engine and interconnected via flexible or hard conduits referred to as xe2x80x9con-board plumbing.xe2x80x9d In systems presently employed in the related art, each component often requires its own mounting strategy and associated fasteners. The on-board plumbing must be routed so as not to clutter the engine. This object is not always met and EGR systems presently used in the field today can be difficult and expensive to service. Further, and because of the ever shrinking space available for the vehicle power plant, the effective use of space through efficient component packaging is a parameter which designers must constantly seek to improve.
Thus, there is a need in the art for exhaust gas recirculation systems which reduce the number of components needed to effectively recirculate exhaust gas to the air/fuel mixture. Further, there is a need for such a system that reduces the complicated on-board plumbing of the type required for vacuum actuated EGR systems. There is also a need in the art for an exhaust gas recirculation system that is easy and inexpensive to service in the field. Finally, there is a need in the art for an exhaust gas recirculation system which has improved response time and accurate repeatability and which is smaller than present systems employed in the related art.
The deficiencies in the related art are overcome by an exhaust gas recirculation system for an internal combustion engine of the present invention. The exhaust gas recirculation system includes a valve body having an exhaust port adapted for fluid communication with a source of exhaust gas, an intake port adapted for fluid communication with the intake manifold of an internal combustion engine, and a valve member movably supported within the body between open and closed positions thereby controlling the flow of exhaust gas from the exhaust port to the intake port. The system further includes a diaphragm housing which is operatively mounted to the valve body and supported thereby. The diaphragm housing defines a vacuum cavity in fluid communication with a source of negative pressure and an atmosphere cavity in fluid communication with a source of second pressure. A diaphragm member is disposed between the vacuum and atmosphere cavities and is operatively connected to the valve member. The diaphragm member is movable in one direction in response to negative pressure induced in the vacuum cavity and in the opposite direction in response to a biasing force to move the valve member between its open and closed position. The exhaust gas recirculation system of the present invention further includes an integrated vacuum regulator. The vacuum regulator is operable to control the movement of the valve member between its open and closed positions by controlling the negative pressure induced in the vacuum cavity. Furthermore, the EGR system of the present invention includes an integrated pressure sensor which senses the difference between the pressure in the vacuum cavity and the pressure at the intake port.
The exhaust gas recirculation system of the present invention results in elimination of a number of components found in conventional EGR systems. For example, there is no need for space or hardware to mount a separate vacuum regulator, or separate pressure sensor employed to sense the difference in pressure between the diaphragm and the intake manifold as well as no need for the associated on-board plumbing typically employed in connection with vacuum actuated EGR systems in the related art. Furthermore, the exhaust gas recirculation system of the present invention is more responsive when compared to the dispersed components that make up comparable systems known in the related art. In addition, the exhaust gas recirculation system of the present invention is relatively small and compact and therefore has improved xe2x80x9cpackagingxe2x80x9d characteristics allowing engine designers greater freedom when positioning the EGR system of the present invention relative to other related engine components.